This is probably too late, but...
Black widows are very shy. They will rarely attack anything but their prey. I say rarely, because obviously there are occasional instances of people getting bit. Bites happen when the spider is cornered, held or being squeezed or if they get wrapped up in their web with a person or animal. I have kept various species of widows for years now and also live with them ...they are very abundant in my yard. I have never been biten. I have even handled them.
Couple of options...
If her web is in an ok place where no one will sit on it, then let her live out her life where she is. Have fun feeding her at night.
To capture her...
Have a cup w/cover or jar ready and a small paint brush or stick. A long handled artist brush is nice because it allows one to push the spider without as much risk of harming her and keeps you from getting tangled up in her web.
At night, wait until she is well out into her web. Use the brush or stick to break all the webbing between her and her hiding place. Be quick with this action! Dont be timid, because they can escape upwards very fast. You will see that the webbing leads upwards towards a hole, crack or some other hiding place. When you cut her off from her den, she will be helpless ...blind so to speak. Use the brush to coax her into the container. She will gladly get into the jar to escape and hide.
Good luck.